The present invention is in the field of friction braking systems. More specifically this invention relates to multiple disc brake systems wherein the discs have slots on their periphery which are used to engage splines.
In brake assemblies which employ a number of brake discs which are alternately splined to the wheel and the axle, the discs are stressed by contact with the splines. This stress can lead to deterioration of the discs periphery. This is especially apparent when the discs are of a carbon composition (as contrasted with the use of steel to form the discs). Prior art has tried to protect the lug portion of the discs (the peripheral portion between the spline engaging slots) from this stress by covering the slots such that the splines contact the covering, instead of contacting the disc directly. For example U.S. Pat. No. 4,511,021 by Grider discloses inserts for this slot. The disclosed insert is flush with the slot, and therefore transfers force directly to the slot walls.
Besides the stress on the discs due to the engagement with the splines, the discs can also deteriorate due to thermal oxidation and catalytic oxidation. Prior art methods have tried to protect the lug portions of the discs by covering the lugs in various ways. For example, U.S. Pat. No. 3,972,395 by Jannasch et al covers the lugs with a woven carbon cloth, which is cured on. An insert is then added to cover the slot portion. U.S. Pat. No. 4,083,434 by Pinter comprises larger segments of protective cover, which cover the lug portion and the slot portion in one piece. Both of these designs also contact the slot wall portions, and thus transfer loads directly to the slot walls.
Prior art methods have also covered the log portion with a U-shaped cap, riveted to the lug, which had a slight overhang to keep the spline from wearing the slot wall. However, the spline would wear away, or deform this overhang in use, leaving no protection for the slot wall.
Tests have shown that the disc carbon material is much stronger when loaded via rivets or other fastening device, instead of being loaded via the slot walls. Therefore a lug protection method and apparatus is desired which would protect the lug from thermal and catalytic oxidation while at the same time protecting the lug from stress loads by not loading the slot wall.